200-201 Network Intrusion Analysis Practice Question
A network analyst is examining a PCAP and notices a series of TCP packets with the PSH flag set and small payload sizes, sent from an internal host to an external IP. The external IP responds with similar small packets. The communication is continuous and occurs at regular intervals. Which type of activity is most likely occurring?
⚠ Common exam trap
The trap here is assuming any regular communication is benign, but the small payloads with PSH and regular intervals are a hallmark of C2 beaconing, not routine traffic like NTP.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Interactive command-and-control session
The combination of small payloads, PSH flag, and regular intervals is indicative of an interactive command-and-control channel. Attackers often use such channels to maintain stealth, sending commands and receiving responses in small packets to avoid detection by volume-based monitoring. This pattern is distinct from bulk transfers or DoS attacks.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Network time synchronization
Why it's wrong here
Network time synchronization typically uses NTP over UDP, not TCP with PSH flags. While NTP can occur at regular intervals, it does not involve small TCP payloads with PSH. The TCP-based pattern here is more consistent with an interactive session than time synchronization.
- ✓
Interactive command-and-control session
Why this is correct
Small, regular packets with the PSH flag set often indicate interactive traffic where data is sent immediately. This pattern is typical of command-and-control (C2) communications, where an attacker sends commands and receives output in small chunks, maintaining a persistent session with periodic check-ins.
- ✗
Denial-of-service attack
Why it's wrong here
A denial-of-service attack would involve a high volume of traffic intended to overwhelm a target, often with large packets or many connection attempts. The small, regular packets described here suggest a low-bandwidth, stealthy communication rather than a flood-based attack.
- ✗
Large file transfer
Why it's wrong here
Large file transfers typically involve larger payload sizes and often utilize full TCP window sizes to maximize throughput. The small payload sizes and regular intervals in this scenario are not characteristic of bulk data transfer, which would show sustained high-volume traffic.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
This 200-201 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 200-201 exam.